This invention relates to a novel drainage quilt for use in a subterranean drainage system. More specifically, this invention relates to a filtered drainage quilt which may be used for removing water from soil around subterranean walls, for distributing water into leach, drainage or irrigation fields, and for a number of other uses where it is necessary to relieve or redirect water and other fluid flow.
When constructing a house or a building with subterranean walls, it is necessary to install a system which facilitates drainage of water away from the subterranean walls. Water must not sit near the foundation of the structure because, over time, the water can degrade the integrity of some waterproofing membranes or damproofing and leak into interior spaces. Most foundations are made of cinder block or poured or precast concrete, and waterproofed with various bituminous or rubber waterproofing membranes or bituminous damproofing materials. The presence of hydrostatic pressure encourages leakage of water through any void or weakness in the membrane or dampproofing, through sub-grade walls and floors to the interior of habitable spaces rendering them nonusable.
Different sources of water which could contribute to the presence of hydrostatic pressure include ground, surface, and roof and gutter water. Ground water must be taken into account when designing below grade spaces. It can be at different elevations at different times of the year. Surface water, generally the largest amount of water that needs to be controlled, comes from rain, melting snow, and drainage from other areas of the building site. Surface water may be diverted away from a house by building the structure on a high point. Additionally, the land surrounding the building is sloped downward in order to direct water away from the building. However, some amount of surface water seeps into the ground, and if not dealt with, will cause or add to hydrostatic pressure buildup.
Roof and gutter water may be routed away from the house in two ways: dispersed on the surface away from the building or piped away underground. Surface dispersal is attractive because it is easy to monitor; most problems that may occur are noticeable and correctable. Surface dispersal is also less expensive than piping. However, even when this method is effective, the water remains near the foundation. As a complement to surface dispersal, the underground system channels the water away from the foundation through a network of subterranean pipes.
The function of a drainage system is to remove water from the soil surrounding a building, while concurrently filtering or preventing movement of soil particles. In the past, removal of ground water and relief from hydrostatic pressure have been accomplished by underground drainage systems which include porous or perforated pipes, such as PVC, and gravel or crushed rock. In these drainage systems, gravel or crushed rock is placed over and around the pipe to relieve hydrostatic pressure and to direct the ground water to the perforated pipe. A filter fabric is placed on top of the gravel to prevent soil from mixing with the gravel and clogging paths to the perforated pipe. Backfill is then placed on top of the filter fabric and in the area next to the subterranean wall.
The filter fabric mentioned above is usually referred to in the art as a geotextile and is typically made up of non-woven fibers, such as polypropylene. The fibers are melted and extruded into continuous filaments, and are then formed into layered sheets and punched with barbed needles that entangles the filaments into a strong bond.
Problems have arisen in connection with the above described conventional drainage system. First, gravel or crushed rock is not readily available in all locals and may be expensive to transport to job sites. Additionally, gravel and crushed rock are heavy and somewhat burdensome and expensive to install at a job site. Finally, the geotextile fabric can be dislodged when placing backfill over the fabric, allowing possible mixing of the dirt and gravel. Dirt may then enter and clog the perforated pipes, thereby rendering the drainage system nonfunctional and providing no relief from hydrostatic pressure to the subgrade walls. Clogging remains a problem even when the system is carefully designed with the particle size distribution of filter media and aggregate media properly matching the native soil in the region to be drained.
Most current drainage systems utilizing geotextile wraps over gravel cores still require careful design and labor intensive installation procedures.
Subterranean drainage quilts are prefabricated and offer many advantages over the gravel/covering systems, including ease of installation and reduction of cost. A number of prior art prefabricated systems have been developed which utilize vertical fins comprising open plastic core surrounded by polymer filter fabric to intercept and channel the underground water into drainage pipes.
Such systems offer substantially more reliable drainage systems, but these systems are hampered by the need for careful installation and labour intensive on-site assembly of the drainage fins and the tubing into continuous lengths. The drainage tube necessarily incorporated into the system is an additional cost component, because the filter cloth covered fins themselves do not provide enough built-in flow capacity, when subjected to lateral soil pressure to conduct water away from the site quickly, without the provisions of the additional pipe or conduit.
Hence, the use of such systems has been restricted to specialized drainage situations where higher on-site installed costs can be tolerated.
A septic tank system receives all waste fluid from a house or small building and delivers the waste fluid to a septic tank. The septic tank then breaks down the waste fluid to liquified sewage and other wastewater by utilizing either anaerobic or aerobic bacteria. The liquified sewage is then piped from the septic tank via drain lines to a leaching field, where the liquid is dispersed into an absorption field.
The pipes which carry the liquid from the septic tank to the leaching field are perforated or porous, such as PVC, and are conventionally surrounded by a mineral aggregate, such as gravel.
The subterranean drainage systems, as described above, may be used in connection with a septic system; however, the aforementioned problems associated with present subterranean drainage systems remain.
The difficulties suggested in the preceding are not intended to be exhaustive but rather are among many which may tend to reduce the effectiveness of prior drainage systems. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that drainage systems appearing in the past will admit to worthwhile improvement.